System and method for processing ultrasonic signals

ABSTRACT

A system and method for eliminating confusion associated with checking valves, wherein additional test points are added to the measurement of a valve for ensuring the verification of the actual sources of leaks or turbulence. A base line measurement for the valve is established by measuring the level of ultrasonic sound at the two points upstream from the valve. The level of the ultrasound at two downstream points is then measured. The value of the ultrasound at the downstream test points is compared to the values of the ultrasound at the upstream test points. If the values of ultrasound at the downstream test points are higher than the values of the ultrasound at the upstream test points, then the valve is leaking. If the values of the ultrasound at the downstream test points are close to or lower than the values of the ultrasound at the upstream test points, then the valve is not leaking, i.e., the valve is good.

RELATED APPLICATIONS

[0001] The present invention relates to, and claims priority of, U.S.patent application Ser. No. 10/292,799, filed on Nov. 12, 2002, entitledSystem for Heterodyning an Ultrasonic Signal, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention generally relates to the field of ultrasonicgenerators and, more particularly, to a system and method for processingheterodyned ultrasonic signals that are generated during valveinspections.

[0004] 2. Description of the Related Art

[0005] It is well known that ultrasonic generators and detectors can beused to locate leaks or defects, e.g., in pipes. Such a system is shownin U.S. Pat. No. 3,978,915 to Harris. In that arrangement, ultrasonicgenerators are positioned in a chamber through which the pipes pass. Atthe ends of these pipes, exterior to the chamber, ultrasonic detectorsare located. At the point where a leak occurs in the pipe or the pipewall is thin, the ultrasonic energy will enter the pipe from the chamberand travel to the end of the pipe where the detector is located. Thedetector will receive an ultrasonic signal at the end of the pipeindicating the existence of the leak or weak spot in the pipe.

[0006] By locating an ultrasonic generator in a closed chamber, astanding wave pattern with peaks and nodes is established. If a nodeoccurs at the position of a leak or weak spot, no ultrasonic energy willescape and the defect will not be detected.

[0007] Ultrasonic sensors have also been used to detect ultrasonicenergy generated by friction within mechanical devices as disclosed inU.S. Pat. No. Re. 33,977 to Goodman, et al., the details of which arehereby incorporated herein, in their entirety, by reference. The greaterthe amount of friction, the greater the intensity of the generatedultrasonic energy. Applying a lubricant to the device reduces frictionand consequently the intensity of the generated ultrasound drops.Measuring ultrasonic energy thus provides a way to determine whenlubrication has reached the friction generating surfaces. Additionally,faulty devices, such as bearings, generate a higher level of ultrasonicenergy than do good bearings and thus, this condition can also bedetected. However, conventional means require two people to perform thisprocedure—one person to apply the lubricant to the device, and oneperson to operate the ultrasonic detector.

[0008] In certain instances, e.g., when detecting the malfunction ofbearings, an ultrasonic detector is mechanically coupled to the casingof the bearings so that the vibrations caused by the malfunction can bemechanically transmitted to it. With such an arrangement, the frequencyis not set by an ultrasonic generator, but is created by the mechanicalvibration itself. Here, an ultrasonic detector circuit must be capableof sweeping over a band of frequencies to locate the one frequency thatis characteristic of the malfunction. This is usually accomplished by aheterodyning circuit which can be tuned to various frequencies, much inthe manner of a radio receiver.

[0009] Since ultrasonic energy used for these purposes is generally inthe range of 40 kHz, it is too high in frequency to be heard by a humanbeing. Thus, means are typically provided for heterodyning, or frequencyshifting, the detected signal into the audio range, and various schemesare available for doing this.

[0010] Ultrasonic transducers generally produce a low voltage output inresponse to received ultrasonic energy. Thus, it is necessary to amplifythe detected signal using a high-gain preamplifier before it can beaccurately processed. However, if low cost heterodyning and displaycircuitry are to be used, means must be made available to attenuate theamplified signal to prevent saturating these circuits when high inputsignals are present. This attenuation also adjusts the sensitivity ofthe device. For a hand-held unit, the degree of attenuation should beselectable by the user. For example, U.S. Pat. No. 4,785,659 to Rose etal. discloses an ultrasonic leak detector with a variable resistorattenuator used to adjust the output level of an LED bar graph display.However, this attenuation method does not provide a way to establishfixed reference points to allow for repeatable measurements.

[0011] U.S. Pat. No. 5,089,997 to Pecukonis discloses an ultrasonicenergy detector with an attenuation network positioned after an initialpre-amplifier and before the signal processing circuitry, which createsan audible output and an LED bar graph display. The resistors in thePecukonis attenuation network are designed to provide an exponentialrelationship between the different levels of attenuation. However,Pecukonis does not heterodyne the detected signals to produce an audibleoutput, but rather teaches the benefits of a more complex set ofcircuits which compress a broad range of ultrasonic frequencies into anarrower audible range. For many applications, the cost and complexityof this type of circuitry are not necessary.

[0012] When using ultrasonic energy to detect leaks, it is useful tohave a portable ultrasonic sensor which indicates the presence andintensity of ultrasonic energy both visually and audibly. U.S. Pat. No.Re. 33,977 to Goodman et al. discloses an ultrasonic sensor thatdisplays the intensity of the detected signal on an output meteroperable in either linear or logarithmic mode, and also provides foraudio output through headphones. U.S. Pat. No. 4,987,769 to Peacock etal. discloses an ultrasonic detector that displays the amplitude of thedetected ultrasonic signal on a ten-stage logarithmic LED display.However, the detector disclosed in Peacock does not process the detectedsignal to produce an audible response, nor does it provide for signalattenuation after the initial pre-amplification stage.

[0013] Means have been proposed for increasing the output of theultrasonic transducer. For example, in U.S. Pat. No. 3,374,663 to Morrisit is suggested that an increase in the voltage output can be achievedby serially arranging two transducers. It has been found, however, thatwith such an arrangement a typical transistor pre-amplifier loads thetransducers to such an extent that the gains achieved by stacking themserially are lost. The Morris patent proposes the use of a tripleDarlington configuration in order to produce a sufficiently high inputimpedance to prevent this degradation in the signal produced by thestack of transducers. Unfortunately, the transducers in this arrangementare not placed so that they both readily receive ultrasonic energy.Thus, the Morris arrangement is not entirely satisfactory.

SUMMARY OF THE INVENTION

[0014] The present invention is directed to providing improved methodsand apparatus for detecting leaks and mechanical faults by ultrasonicmeans. In accordance with the invention, an input transducer signal isapplied to a unity gain buffer amplifier that is used to maintain theimpedance level seen by the transducer. The processed signal from theunity gain buffer amplifier is supplied to a voltage control amplifierthat also receives a voltage control signal that is generated by adigital-to-analog converter located on an external I/O board. Thevoltage control signal is used to switch the voltage controlledamplifier such that the dynamic range of the signal is expanded prior toa clip of the signal. The voltage control signal is based on a levelthat is programmed into the voltage control amplifier by thedigital-to-analog converter located on the external I/O board. Thevoltage controller is thus controlled by the I/O board in response tocommands sent to the external I/O board from a micro-controller.

[0015] The output from the voltage controlled amplifier is connected toa fixed gain differential amplifier. The output signal from the fixedgain amplifier is supplied to a variable gain amplifier that isswitchable between two fixed levels, such as 0 dB and 20 dB. The gainlevel of the variable gain amplifier is toggled between the two fixedgain levels based on a level that is determined by the amount of gainthat is programmed into the voltage control amplifier.

[0016] The output of the variable gain amplifier is supplied to a pairof heterodyning circuits, i.e., a dual heterodyning circuit. At eachrespective heterodyning circuit, the output signal from the variablegain amplifier is multiplied with a local oscillator signal that isinternal to each circuit. Here, each local oscillator is nominally setto 38 kHz such that for a 40 kHz input transducer signal, a differencefrequency of about 2 kHz (i.e., the audio component) is provided at theoutput of each heterodyning circuit.

[0017] The output signal from the first heterodyning circuit isamplified and divided into two signal branches. The first signal branchis transformer coupled to a headphone output. The second signal branchis connected to an amplifier that is also transformer coupled to a lineoutput and also applied to an external audio amplifier. The output fromthe second of the heterodyning circuits is amplified and supplied to ametering circuit.

[0018] In addition, a further analog signal path is created at thesecond heterodyning circuit. The signal in this path is converted to alinear dB format analog signal and supplied to a micro-controller. Thisanalog signal is converted in the micro-controller into a digital signalby an analog-to-digital converter, and is further converted in themicro-controller into a WAV file format, as well as other digital signalformats, for subsequent spectral analysis.

[0019] The present inventors have determined that a heterodyned signalthat drives a meter requires a relatively large dynamic range, but alimited frequency response, while a heterodyned signal that is requiredfor headphones or spectral analysis may have a low dynamic range, butrequires high resolution. Further, it has been found that the resolutionor frequency response of the input transducer signal is degraded if asingle heterodyning circuit is used to drive a number of circuits ormeters with competing requirements. In order to overcome these competingrequirements, the present invention uses a dual heterodyning circuit inwhich the two individual heterodyne circuits are separately optimized sothat the second results in a signal with a large dynamic range and thefirst results in a signal with a great resolution, and neither undulyloads the transducer array or obscures subtle frequency components. Thispermits the capture of particularly low level frequency components forextraction during spectral analysis.

[0020] In accordance with the invention, the first heterodyning circuithas a feed back loop filter and a transformer to provide an enhancedspectral (i.e., frequency) response. This circuit is used to drive theheadphone, a wave file generator and a line output. This signal, whichhas a modest dynamic range but a high frequency response and a lowsignal to noise ratio, allows the spectrum of the signal to be analyzedin real time by an external spectrum analyzer, recorded for lateranalysis or listened to in real time through the headphones.

[0021] The second heterodyning circuit has a smaller frequency responsebut a larger dynamic range so that it can drive the meter. In accordancewith the invention, the second heterodyne circuit is not required tohave an optimized spectral response. If the meter were driven with thefirst heterodyne circuit, the impedance and dynamic range requirementsof the meter would adversely affect the response. Thus, two heterodynecircuits are used, with the circuit that drives the meter being simpler,and less costly to manufacture and having a larger dynamic range.

[0022] In either mechanical analysis or electrical equipment analysis, alarge number of frequencies in the low frequency range become lost. Thisis especially true in the case of electrical applications. Afterextended use of the detection equipment, operators often tend to beginto use their ears as a guide to the condition of an area of concern.However, it is extremely difficult for a person to discern with theirears the differences between inputs that are electrical in nature andinputs that are vibrational. Further, in other technologies, such asvibration analysis, infrared technologies, or where rotational equipmentis used, the use of the human ear is a highly unreliable way in which topredict faults. For example, a transformer resonating at 60 Hz may causea component in an equipment cabinet to resonate at the same 60 Hz. Whenan operator listens to the cabinet containing the component that isvibrating at the 60 Hz, it is impossible to determine whether theresonance is electrical or mechanical.

[0023] Typically, on/off valves are checked for their position, e.g.,open or closed, or for leakage in the closed position. By way of acontact module, such valves can be tested using the portable ultrasonicdevice of the present invention. Contact modules are generally used todetect structure borne ultrasound. Transducers are contained in themodule, and a rod is attached to the ultrasonic device. The rod acts asa waveguide that conducts ultrasound to excite the transducers togenerate a signal that the ultrasonic device can measure.

[0024] A high level of confusion occurs when checking valves for leaksor “bypassing” caused by turbulent flows, either upstream or downstreamfrom the valve in question. When measurements are performed at adistance from the valve, confusion can arise because an operator isunable to determine whether the valve is good or bad. This occursbecause the operator is unable to distinguish between problems thatoccur at the remote location and those which occur at the or whether thevalve itself. In addition, if the user only checks the upstream anddownstream sides of a valve, then confusion may arise because they maybelieve the valve is “bypassing” and thus, change the valve. A valve isbypassing if fluid (gas or liquid) passes through the valve when it isclosed.

[0025] If the operator falsely concludes that the downstream reading ishigher than the upstream reading, which is usually indicative of aleaking valve, the confusion caused can be extensive in terms of thetime and cost for replacing a valve that is not defective and is not thesource of the potential problem. The actual source of the higher readingfor the upstream side of the valve can originate from turbulencegenerated further down the piping from the valve, such as fromturbulence caused by a right angle connection or even from a partialblockage of the pipe. The method of the present invention eliminatessuch confusion associated with checking valves by adding additional testpoints with which to ensure verification of the actual source of leaksor turbulence.

[0026] In accordance with the method of the invention, this is achievedby establishing a base line measurement for each valve under test. Theultrasonic sound at multiple points upstream and downstream from thevalve is measured. In the preferred embodiment, the ultrasonic sound attwo upstream points and two downstream points is measured. Prior toperforming all measurements, a visual inspection of the valve isperformed to confirm that the valve is closed or in the off position.

[0027] The measurement of the ultrasonic sound at the first upstreampoint is then made at a distance located X times the pipe diameter fromthe valve. The measurement of the ultrasonic sound at the secondupstream point is made at a point located directly upstream of thevalve, approximately at the pipe fitting. The two downstream measurementpoints are at a distance of equal relationship to the upstream testpoint, i.e., the first downstream measurement point is located at adistance located X times the pipe diameter from the valve, and thesecond downstream measurement point is located directly downstream ofthe valve, approximately at the pipe fitting. In the preferredembodiment, X is six (6), i.e., the first measurements are located at apoint that is 6 times the diameter of the pipe away from the valve.

[0028] While touching the contact module to a measurement point tomeasure the ultrasonic energy at the two upstream points, thesensitivity of the dual heterodyning circuit is adjusted by turning arotary knob on the rear of the portable device so that a liquid crystaldisplay, also on the rear of the portable ultrasonic device, displaysthe dB value of the ultrasonic measurements. These initial upstreamultrasound values establish baseline measurements for the valve. Thevalue of the ultrasonic sound at the first and second upstream pointsshould be close to each other. In some circumstances, the secondmeasured ultrasonic value can be slightly lower than the first measuredultrasonic value. In contemplated embodiments, the second measurement isperformed without re-adjusting the sensitivity of the dual heterodynecircuit.

[0029] The level of the ultrasound at the two downstream points is thenmeasured. The value of the ultrasound at the first downstream test pointis compared to the values of the ultrasound at the upstream test points.The value of the ultrasound at the second downstream test point ismeasured to ensure that no ultrasonic sound is emanating downstream fromthe valve. If the value of the ultrasonic sound measured at the seconddownstream point is greater than the value of the ultrasonic soundmeasured at the first downstream point, then this ultrasonic sound mustbe “tuned out” or “shut off” to obtain a proper test of the valve. Whenit is not possible to tune out or shut off a downstream structure borneultrasound, it is necessary to locate the source of the highest readingto determine its effect on the outcome of the measurements.

[0030] In accordance with the embodiments of the invention, additionalultrasound measurements further downstream are performed to assist inlocating/confirming the source of the ultrasound. Hence, if the valuesof the ultrasound at the downstream points are higher than the values ofthe ultrasound at the upstream points, the valve is leaking. On theother hand, if the values of the ultrasound at the downstream points areclose to or lower the values of the ultrasound at the upstream points,then the valve is not leaking, i.e., the valve is good.

[0031] By using the dual heterodyning circuit of the present inventionto provide the enhanced spectrum, it becomes clear whether a detectedresonance is mechanical or electrical. In addition, fault frequenciesare also more easily discernable. In other words, the enhanced signaloutput provides a lower signal-to-noise ratio, so as to increase theease with which frequency components are analyzed. In addition, themethod of the invention eliminates the unnecessary replacements of“good” valves, which can be expensive in certain environments, such asin a nuclear plant or on a ship, where the valves are welded into place.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The foregoing and other advantages and features of the inventionwill become more apparent from the detailed description of the exemplaryembodiments of the invention given below with reference to theaccompanying drawings in which:

[0033]FIG. 1 is an exemplary block diagram of the dual heterodyningcircuit in accordance with the present invention;

[0034]FIGS. 2A through 2K is a schematic diagram of the dualheterodyning circuit shown in FIG. 1;

[0035]FIG. 3(a) and FIG. 3(b) form a block diagram of the I/O board, themicro-controller, and the rear panel in accordance with the invention;

[0036]FIG. 4 is a block diagram illustrating a flash card inserted intothe micro-controller of FIG. 3(a);

[0037]FIG. 5 is a bottom view of the ultrasonic instrument of thepresent invention;

[0038]FIG. 6 is a perspective view showing the flash card and rear panelof the ultrasonic instrument of the invention;

[0039]FIG. 7 is a plan view of the rear panel of the ultrasonicinstrument of the invention;

[0040]FIG. 8 is a front view of the ultrasonic instrument of theinvention;

[0041] FIGS. 9(a) and 9(b) are block diagrams of an additional aspect ofthe invention;

[0042]FIG. 10. is an illustration of an exemplary network of piping inwhich the method of the invention is implemented; and

[0043] FIGS. 11(a), 11(b) and 11(c) are a flow chart illustrating thesteps of the method of the invention.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0044]FIG. 6 is a perspective view of a portable ultrasonic detector600. Toward the front of the housing there are ultrasonic transducers95, as shown in FIG. 8. Micro-processor controlled circuits forheterodyning the ultrasonic signal to shift its frequency to the audiorange are contained in the body of the housing. A display 82 is locatedat the back so the operation and the results can be viewed. At the back,there is also a jack 88 for headphones, so that the user can listen tothe audio sound during a test, e.g., as a way of locating a leak. Otherjacks and controls are located on the body or will be describedsubsequently.

[0045]FIG. 1 is an exemplary block diagram of the dual heterodyningcircuit in accordance with the present invention which is located in thehousing of the ultrasonic detector. In FIG. 1, an input signal isapplied from an ultrasonic transducer to a buffer amplifier 12 (U4B) atinput 11 (P10). Typically, unity gain buffer 12 is used to maintain at adesired level the impedance level seen by the transducer. The processedsignal from buffer 12 is supplied to voltage controlled amplifier (VCA)14 (U5) that also receives a voltage control signal 15 that is generatedby a digital-to-analog converter on an external I/O board shown in FIG.3(b). The voltage control is thus controlled by the I/O board inresponse to commands sent to the external I/O board from amicro-controller (see FIG. 3(a)).

[0046] Voltage controlled amplifier 14 is connected to a fixed gainamplifier 16. In preferred embodiments, amplifier 16 has a fixed gain ofapproximately 20 dB. The output signal from amplifier 16 is supplied tovariable gain amplifier 18 (VGA) that is switchable between two fixedlevels, such as 0 dB and 20 dB. The gain level of amplifier 18 istoggled between the two fixed gain levels based on a signal levelapplied to input 17. This signal is determined at the micro-controlleron the I/O board based on the amount of gain that is programmed into thevoltage controlled amplifier 14.

[0047] The output of VGA 18 is supplied to a first heterodyning circuit20 (U8). In heterodyne circuit 20, the output signal supplied to VGA 18is multiplied in multiplier 22 by a local oscillator 21 that is internalto heterodyne circuit 20. Sum and difference frequencies are provided atthe output of circuit 20. At this point, the high frequency componentsof the signal are filtered out and a difference signal is buffered inamplifier 24, such that an audio signal is provided. The localoscillator 21 within circuit 20 is nominally set to 38 kHz such that fora 40 kHz input transducer signal, a difference frequency isapproximately 2 kHz. Amplifier 24 is used to amplify the output signaland apply it to terminal 23 which leads to a metering circuit (notshown). This signal has a large dynamic range.

[0048] The output signal from VGA 18 is also received by amplifier 30,which amplifies this signal prior to supplying it to a secondheterodyning circuit 32. In exemplary embodiments, the signal suppliedto amplifier 30 is amplified by approximately 10 dB. The secondheterodyne circuit 32 receives the output of amplifier 30 and multipliesthis signal in multiplier 33 by a local oscillator 34 that is alsointernal to circuit 32. Sum and difference frequencies are created atthe output of heterodyne circuit 43. The high frequency components ofthe signal are filtered out and the low frequency signal is buffered inamplifier 35, such that an audio signal is provided. The localoscillator within circuit 32 is nominally set to 38 kHz such that for a40 kHz input transducer signal, a difference frequency audio signal isapproximately 2 kHz. The audio signal is then buffered by a unity gainamplifier 36. The output of amplifier 36 is next provided to anamplifier 37. In preferred embodiments, the signal level supplied toamplifier 37 is increased by approximately 40 dB.

[0049] In accordance with the invention, the second heterodyning circuit32 has a feed back loop 31 from the output of amplifier 35 to the inputof circuit 32. This feedback loop 31 provides an enhanced spectral(i.e., frequency) response.

[0050] The output signal from unity gain amplifier 36 is divided intotwo signal branches. The first branch leads to the amplifier 37. Thesecond branch leads from unity amplifier 36 to amplifier 40 that iscoupled to a headphone output by way of transformer 41. In the firstsignal branch, amplifier 37 is coupled to transformer 36, which in turnis coupled to a line output. The line output is subsequently applied toan audio amplifier (not shown). In addition, a further analog signalfrom amplifier 37 is coupled to amplifier 38, where it is attenuated byapproximately −3 dB. The attenuated signal is then supplied to themicro-controller (not shown). This analog signal is converted in themicro-controller into a digital signal by an analog-to-digitalconverter, and is further converted in the micro-controller into a WAVfile format, as well as other digital signal formats for storage andplayback, and for subsequent spectral analysis.

[0051] The wideband, high resolution signal from amplifier 36, which isa result of feedback loop 31, is used to drive the headphone, a wavefile generator and a line output. This signal, which has a modestdynamic range but a high frequency response and a low signal to noiseratio, allows the spectrum of the signal to be analyzed in real time byan external spectrum analyzer, recorded for later analysis or listenedto in real time through the headphones.

[0052] The first heterodyning circuit 20 has a smaller frequencyresponse but a larger dynamic range so that it can drive the meter. Inaccordance with the invention, the first heterodyne circuit is notrequired to have an optimized spectral response. If the meter is drivenwith the same heterodyne circuit as the headphone circuit, the impedanceand dynamic range requirements of the meter would adversely affect theheadphone response. Thus, two heterodyne circuits 20, 32 are used, withthe circuit that drives the meter being simpler, less costly tomanufacture and having a greater dynamic range. The circuit that drivesthe headphones has a smaller and a lower signal-to-noise ratio, whichprovides a better spectral response.

[0053] By way of example, FIGS. 2A-2K are an exemplary schematic diagramof the dual heterodyning circuit in accordance with the presentinvention. Buffer amplifier 12 is shown in FIG. 2A. A transducer signalhaving a frequency of approximately 40 kHz±5 kHz is applied viaconnector 11 (P10) by way of capacitors 210 (C27) and 211 (C21),resistors 212 (R20) and 213 (R27), diodes 214 (D2) and 215 (D3) to thebuffer amplifier 12, which is used to maintain the impedance level seenby an input transducer (not shown) at a predetermined fixed level.Typically, amplifier 12 is a standard Integrated Circuit (IC), such asan OP-284ES.

[0054] The voltage divider comprising resistors 220 (R36) and 221 (R45),along with capacitor 222 (C41) are coupled to the positive input ofamplifier 44 (U10) that is used to generate a 6 volt low impedanceoutput based on the 12 volt input that is applied to resistor 220. The 6volt low impedance output is used to provide a reference level for theanalog circuitry of the invention. Amplifier 44 has a feed back loopcomprised of capacitor 222 (C25) and resistor 223 (R33) to improve itsresponse. This amplifier is typically a standard “off-the-shelf” IC,such as an AD797 manufactured by Analog Devices.

[0055] Capacitor 230 (C19) and resistor 232 (R24) are connected inseries from the output of amplifier 12 to the input of voltagecontrolled amplifier (VCA) 14 (U5). Amplifier 14 with capacitors 234(C24), 236 (C14), 238 (C33), resistors 240 (R21), 242 (R30) provides ameans for expanding the dynamic range of the signal prior to clipping ofthe signal. Preferably, VCA 14 is a standard voltage controlledamplifier, such as a SSM2018T manufactured by Analog Devices. Thecontrol voltage on pin 11 of VCA 14 is generated by a digital-to-analogconvertor 71 (DAC) that resides on an I/O board (shown in FIG. 3(b))that is controlled by an external micro-controller (shown in FIG. 3(a)).VOS 302 is the control signal. The output of VCA 14 is on pin 3 throughcapacitor 236 and resistor 240 (TP5).

[0056] As shown in FIG. 2B, the output of VCA 14 on TP5 is applied tothe input of the differential amplifier 16 through capacitor 242 andresistor 244. A feed back loop of capacitor 246 and resistor 248 isconnected around amplifier 16. Capacitor 249 and resistors 245, 247 formthe rest of the differential amplifier 16. Amplifier 16 has apredetermined fixed gain level and because of its high common moderejection ratio noise is reduced. The output signal from amplifier 16 iscoupled to the input of variable gain amplifier 18 by way of capacitorC18 and resister R23. In preferred embodiments, amplifier 16 istypically a standard “off-the-shelf” IC, such as an OP-284ES, and has again level of approximately 20 dB.

[0057] Amplifier 18 is switchable between two gain levels based on thesensitivity level required by VCA 14. In preferred embodiments,amplifier 18 is switched between 0 dB and 20 dB by an analog switch 45(U3) that is typically a standard “off-the-shelf” IC, such as a DG419DY.Resistor 254 (R19), resistor 256 (R15) and variable resistor 258 (VR1)set the gain, while resistor 260 when shorted across the other resistorby switch U3 sets the second gain level The output of amplifier 18 isconnected through capacitor 262 (C20) to the output at TP3. This levelis biased by a voltage from variable resistor 264 (VR2).

[0058] The micro-controller sets the digital bits DAC, CLK, DACSDO,DACLD on connector J3 (FIG. 3(a)). These bits are applied to DAC 71(FIG. 3(b)), which in turn produces the control voltage 302 (VOS or VOF)on J13. A control voltage 302 VOS is received on P13 (FIG. 2H). As shownin FIG. 2G, VOS is then supplied to amplifier 52 (U11A) by way ofresistors 270 (R57) and 272 (R58) to amplifier 57 by way of resistor 274(R83). The output of amplifier 52 is provided to one input ofdifferential amplifier 53. A unity gain buffer amplifier 55 has an inputvoltage from variable resistor 276 (VR7). Its output is applied to theother input of amplifier 53 as a reference voltage. The output ofamplifier 53 is amplified in amplifier 54 and provides the signal atTP12. In effect, the amplifiers 52, 53, 54 and 55 scale and level shiftthe VOS signal. As can be seen from FIG. 2A, the TP12 signal is appliedto the control output of VCA 14.

[0059] The VOS signal level is from approximately 0 to 5 volts. Inpreferred embodiments, the signal level of VOS is from 0 to 4.095 volts.

[0060] In alternative embodiments, variable resistor 280 (VR8) RT1, andRG1 (FIG. 2G) are optionally connected for providing nominal temperaturecompensation of the system.

[0061] Amplifier 57, which also receives the VOS signal, buffers thatsignal and feeds the positive input (pin 3) of amplifier 56 (U14A)through resistor 284 (R82), where amplifier 56 is connected in acomparator arrangement. Here, resistor 286 (R84) is used to providehysteresis for noise rejection. Coupled to the negative input (pin 2) ofamplifier 56 is a variable reference level that is created by variableresister 288 (VR9), which sets a reference level. Typically, amplifiers52, 53, 54 and 55 are standard “off-the-shelf” ICs, such as a LM6134AIM.

[0062] In accordance with the invention, the reference level that isapplied to the negative input (pin 2) of amplifier 56 is set during acalibration process to generate a CLIP signal that is output from pin 1of amplifier 56. This CLIP signal is used to switch the variable gainamplifier 18 from 0 dB to +20 dBs. (See the input switch to switch 45 onFIG. 2B.) Simultaneously, the gain of the transducer pre-amps (notshown) is decreased by 20 dB. Of note, in order to extend the dynamicrange of the transducer amplifier (not shown), the overall gain of thesystem plus the transducer pre-amp must have no net increase in gain. Asa result, if the variable gain amplifier in the pre-amp located withinthe transducer has a 100 dB dynamic range and a pad of 20 dB isinserted, then a clean, un-clipped dynamic range of 120 dB is achievedfrom the entire system. The signal that controls the switching ofamplifier 18 is the CLIP signal that is generated by amplifier 56.

[0063] Amplifier 56 is controlled by a sensitivity setting such that theoverall sensitivity of the system is determined by the micro-controllerwhereby an operator using a controller 72 on a front panel of theinstrument 600 can adjust the overall sensitivity (see FIG. 5 and FIG.7). As a result, if the sensitivity of the system is lowered by apredetermined level, the clip signal output from amplifier 56 is toggledsuch that gain switching occurs at the transducer pre-amp and atvariable gain amplifier 18. In preferred embodiments, the predeterminedlevel is 10 dB downward from the maximum sensitivity of the system.

[0064] With reference to FIG. 2A, differential amplifier 43 (U4A)receives the output 268B of variable gain amplifier 18 (FIG. 2B) on itspositive input 241 (pin 3). This signal is received through resistors251 (R13) and 253 (R17), and capacitor 255 (C10). The output ofamplifier 43 is connected to zener diode 259 (D1) at TP1. Amplifier 43functions as a positive rectifier circuit outputting a positive DCvoltage proportional to the amplitude of the signal. Zener diode D1clamps the output of amplifier 43 to a voltage of approximately 5 voltsto prevent the micro-controller from being subjected to excessivevoltage levels. As a result, a DC voltage is generated which themicro-controller compares to a predetermined value. If the DC voltage isgreater than the predetermined value then the micro-controller indicatessaturation on the LCD display by displaying an over range condition.

[0065] The output of amplifier 18 is also applied to the first of a pairof function generator circuits that form the dual heterodyne circuits 20(U8), 32 (U99), FIG. 2F. The output of amplifier 18 is further connectedto resistor 130 (R8) that is connected in series with capacitor 135(C5), which is subsequently connected to the base of transistor 134 (Q1)(FIG. 2C). The collector of transistor 134 is capacitively connected tothe input (pin 1) of the second of the pair of function generatorcircuits, i.e., heterodyne circuit 32 (U99) (see FIG. 2F) by way ofcapacitor 136 (C3). As shown in FIG. 2C, a feed back loop comprisingcapacitors 140 (C12), 142 (C11), transistor 47 (Q2) and variableresistor 144 (VR14) provides a feedback signal at pin 1 of functiongenerator (heterodyne) circuit 32 (see FIG. 2F). In accordance with theinvention, transistor 46 amplifies the output signal from amplifier 18by a predetermined amount. In the preferred embodiment, thepredetermined amount is 10 dB.

[0066] Ultrasonic signals leaking from a container (not shown) aredetected by the transducer (not shown), amplified and frequency shiftedsuch that a user is provided with an indication of the existence of aleak by way of the sound heard in a pair of headphones (see FIG. 2K).The actual frequency shift of the ultrasonic signal is accomplished inthe function generator 32. The generator (FIG. 2F) may be acommercially-available integrated circuit, such as the EXAR 2206, whichhas been wired to produce sine wave outputs at a frequency determined bytuning resistor 180 (VR3) connected to pin 7 of circuit 32, resistors181 (R46) and 182 (R49) connected from pins 15 and 16 to ground,capacitors 183 (C38), 184 (C43), and resistor 186 (R52). Onecharacteristic of circuit 32 is that a particular bias applied to itsinput (pin 1) will cause it to produce an amplitude-modulated (AM),suppressed-carrier output. The bias to obtain this suppressed-carriermodulation is derived from variable resistor 144 (VR14) (FIG. 2C). Ifcapacitor 183 (C37) and resistor 180 (VR3) are selected to produce acarrier signal that differs from the ultrasonic signal by a frequency inthe audio band, the output of heterodyne circuit 32 will be an audiosignal related to the input ultrasonic signal and a much higher signal.In particular, the output signal will be equivalent to the sum anddifference frequencies of the ultrasonic signal and the carrier signalgenerated within circuit 32, but the carrier signal itself will not bepresent in the output. If, for example, variable resistor 180 (VR3) isset such that circuit 32 generates a 42 kHz signal and the ultrasonicsignal applied through capacitors C3 to circuit 32 is at 40 kHz, theoutput will be at 2 kHz and at 82 kHz. In preferred embodiments, theoscillator in circuit 32 is adjusted between a range of 20 kHz and 100kHz.

[0067] Although a proper bias on the input to circuit 32 will eliminateor suppress the carrier generated by that circuit, it has been foundthat this adjustment is critical and some carrier may leak through dueto temperature and voltage variations. Also, as the carrier frequency ischanged due to changes in the setting of resistor 180 (VR3), there arechanges in the circuit operation that may cause the carrier to appear inthe output unless there is an adjustment of the bias. In order toprovide this adjustment, a servo or feedback network is provided.

[0068] In particular, the output of circuit 32 is also capacitivelycoupled to the base of transistor 35 (Q3) by way of capacitor 190 (C36),and resistor 192 (R40), as shown in FIG. 2F. Together these componentsprovide an input signal for the feedback network formed by transistor 47that biases pin 1 of circuit 32 (see FIG. 2C). Here, transistor 35provides amplification of the output signal from pin 2 of circuit 32 bya predetermined amount. In preferred embodiments, the predeterminedamount of amplification is 40 dB.

[0069] The output from pin 2 of circuit 32 is also fed to voltageamplifier 36 (FIG. 2E), where the signal from pin 2 is buffered. By wayof resistor 171 (R140), the output signal from amplifier 36 feeds thebase of transistor 37 (Q6) over line 304, by way of capacitor 305 (C66)(FIG. 21). Here, the output signal from amplifier 36 is coupled totransformer 39 to thereby generate a low frequency output (“LFO”). Theaudio signal on line 304 is also applied to summing amplifier 68 (FIG.2K) which in turn drives amplifier 40. Amplifier 40 drives transformer41 which is used to power the headphones. In preferred embodiments ofthe invention, transformer 39 has a turns ratio of approximately 1:0.05,and the output signal is used to drive low impedance loads. Thetransformer 41 has a turns ratio of 1:0.175.

[0070] The output signal from amplifier 36 (FIG. 2E) is also provided toamplifier 50, where it is attenuated by approximately −3 dB, based onresistors 300 (R34) and 302 (R26). Amplifier 50 (U1B) and amplifier 36are typically standard “off-the-shelf” ICs, such as an OP-284ES. Theoutput from amplifier 50 is supplied to the micro-controller forconversion into a digital signal by an analog-to-digital converterlocated in the micro-controller (not shown). This digital signal isconverted into a digital format, such as a WAV file, for subsequentimage processing.

[0071] Signals VR and +12VR are applied from a power supply (FIG. 2K) tothe circuit of FIG. 2I. These signals are applied to the negative andpositive terminals of differential amplifier 59 (U12B). Capacitor 306(C48) and resistor 308 (R70) are connected to form a feedback loop aboutamplifier 59. The signal +12VR is applied to the positive input ofamplifier 59 through resistors 310, 311 and 312 (R81). A zener diode 314(D5) is connected between resistors 310 and 311. VR is connected to thenegative input of amplifier 59 through resisters 315 (R68) and 316(R69). The output of amplifier 59 is connected to zener diode 318 (D4),and through resister 319 (R76) to the positive input of amplifier 60(U12A). A variable resistor 320 (VR6) is connected to amplifier 60 andserves to establish a reference point of amplifier 60.

[0072] Signal +12V1 is applied from the power supply (FIG. 2K) to thebias amplifier shown in FIG. 2D. This 12V signal is applied to the VINterminal of voltage regulator 48 (U2). The output (VOUT) of voltageregulator 48 provides a +5 volt TTL signal that is supplied to amplifier49 (U1A) by way of resistors 360 (R6), 362 (R9), and capacitors 364 (C7)and 365 (C8). Amplifier 49 provides a regulated +2.5V voltage that isused as a reference voltage in accordance with the invention. The +5Vvoltage is also used to provide a TTL reference level to all othercircuit ICs where required.

[0073] With further reference to FIG. 2I, amplifiers 59 and 60 provide acomparator circuit that generates a low battery monitor. By way of zenerdiode D5, a regulated reference voltage is generated and applied to thepositive input (pin 5) of amplifier 59. Concurrently with application ofthe regulated reference voltage, a battery voltage is applied to theresistive divider (315, 311) on the negative side (pin 6) of amplifier59. The reference voltage at zener diode D5 remains relatively constantdue to the clamping action of the zener diode D5.

[0074] Zener diode D4 in FIG. 21 is connected to the output of amplifier59, and clamps the output voltage to approximately 5 volts such that themicro-controller is not subjected to excessive voltage levels. If thebattery voltage falls below a predetermined level, then the inputvoltage at the negative input of amplifier 59 will also fall below thereference level. In accordance with the invention, the output ofamplifier 59 is zero to indicate a fully charged battery, andapproximately 3.5 volts to 4 volts (nominal) to indicate that thebattery capacity is low and needs to be recharged. The output ofamplifier 59 is inverted in amplifier 60 and produces the OFF signalused in the circuit of FIG. 2H, as will be explained subsequently. As aresult, a means is provided for the micro-controller to indicate on anLCD whether or not the battery is adequately charged. In preferredembodiments, amplifiers U12A and U12B are standard “off-the-shelf” ICs,such as an LM6132.

[0075] In the contemplated embodiments of the invention, the LCD is ascreen that is large so that the display can easily be seen by theoperator. In accordance with the contemplated embodiments, this wouldinclude a time series display of the heterodyned ultrasonic signal topermit the viewing of measurement trends in real time.

[0076] Returning to FIG. 2E, when the battery level falls below theoptimum operating level, the base of transistor 73 (Q4) is pulled highby the output of amplifier 60 (FIG. 2I) on line 322. This causes theplus input of amplifier 36 to be low. As a result, the output signalfrom amplifier 50 is also low.

[0077] As stated previously in connection with FIG. 1, the first outputfrom amplifier 18 is applied to the first of the pair of functiongenerator circuits, e.g., circuit 20 (see FIG. 2F). This generator mayalso be a commercially available integrated circuit, such as the EXAR2206, which has also been wired to produce sine wave outputs at afrequency determined by tuning resistor 330 (VR5) connected to pin 7 ofthe circuit 20, resistor 331 (R51), capacitor 332 (C42), as well ascapacitor 333 (C37) connected between pins 5 and 6, and resistors 334(R43) and 335 (R48) connected to ground from pins 15, 16 of circuit 20.

[0078] Function generator circuit 20 multiples the first output signalusing an oscillator that is internal to circuit 20. In a manner similarto circuit 32, the sum and difference frequencies of the ultrasonicsignal are also generated at the output pin 2 of circuit 20. Inpreferred embodiments, the local oscillators in circuit 20 and circuit32 are nominally set to 38 kHz. As with the tuning resistor 180 (VR3)that is connected to circuit 32, if tuning resistor 330 (VR5) is setsuch that circuit 20 generates a 42 kHz signal and the ultrasonic signalapplied is at 40 kHz, the output at pin 2 of circuit 20 will be at 2 kHzand at 82 kHz. Since only the audio band signal is desired, the filtercircuit comprising resistors R38, R39, R42 and R44, capacitors C35, C40and C39 will eliminate the 82 kHz sum signal. In preferred embodimentsthe oscillator in circuit 20 is adjusted between a range of 20 kHz and100 kHz.

[0079] Frequency control of function generator circuits 20 and 32 isachieved by the micro-controller 80 (see FIGS. 3(a) and 3(b)). As shownin FIG. 2F, an input signal 302 VOF is applied to the positive input(pin 5) of amplifier 51 (U7B). VOF 302 originates from the DAC 71 whichis on the I/O board (FIG. 3(b)). The voltage level of VOF is fromapproximately 0 to 4.095 volts. The oscillation frequency of circuit 20and circuit 32 is set during a calibration process by way of variableresistors 330 (VR5) and 180 (VR3) (see FIG. 2F). In accordance with theinvention, when the frequency of the system is tuned, voltage VOF ischanged, i.e., the voltage applied to pin 5 of amplifier 51 is changed(FIG. 2F). As a result, the frequency of the local oscillators ofcircuit 20 and circuit 32 can be changed in the range from approximately20 kHz to 100 kHz.

[0080] In accordance with the invention, the output from heterodynecircuit 20 (FIG. 2F) is provided to amplifier 24 on line 340, as shownin FIG. 2H. Connected to amplifier 24 are resistors 345 (R73), 344(R65), and capacitors 342 (C47), and 346 (C53). The output signal meter(pin 1) of amplifier 24 is provided to an additional circuit forconversion into RMS units and dB units (see FIG. 2J). The collector oftransistor 74 (Q5) (FIG. 2H) is connected to the positive input ofamplifier 24, while the base of transistor 74 is connected throughresistor 348 (R80) to OFF signal output from amplifier 60 FIG. 2I). As aresult, when the battery level falls below the optimum operating level,the base of transistor 74 is pulled high and the output signal fromamplifier 24 is terminated. Typically, amplifier 24 is a standard“off-the-shelf” IC, such has an OP-284ES.

[0081] The output signal meter (pin 1) of amplifier 24 shown in FIG. 2His provided to the input of amplifier 61 (U9B) by way of connector J11(FIG. 2J). Connected to the positive input (pin 5) of amplifier 61 areresistors 400 (R106) and 405 (R107). A low pass filtered output signalfrom amplifier 61 is provided to the positive input (pin 3) of amplifier62 (U9A) through capacitor 411 (C74) where it is buffered and outputfrom pin 1 of amplifier 62 over resistor 420 (R105) and capacitor 423(C72) to pin 15 of RMS-to-DC convertor 65 (U19). Typically, amplifiers61 and 62 are standard ICs, such as an OP-284ES. RMS-to-DC convertor 65is typically a standard “off-the-shelf” IC, such as an AD637manufactured by Analog Devices.

[0082] With further reference to FIG. 2J, RMS-to-DC convertor 65computes the root-mean-square, or the mean square of the absolute valueof the input signal at pin 15 of converter 65 and provides an equivalentdc output voltage at pin 16, as well as an RMS output at pin 11. The DCoutput voltage at pin 16 of converter 65 varies linearly to the dB levelof the input signal's amplitude at pin 15 of converter 65. Here, the dcoutput voltage is a buffered output that is provided to amplifier 67(U17A) by way of resistor 426 (R110) and resistor temperaturecompensator 429 (RT1).

[0083] Resistors 432 (R111), 435 (R108) and variable resistor 438 (VR10)are coupled to amplifier 67. Together, these resistors control the gainof amplifier 67 to thereby scale the dB level of the output signal thatis seen on connector J11. Here, R108 is not installed so VR10 completelycontrols the scaling of the dB output signal from amplifier 67. Thisoutput signal is forwarded by way of pin 1 (TP21) on connector J11 tothe I/O board shown in FIG. 3(b) and the micro-controller shown in FIG.3(a).

[0084] As further shown in FIG. 2J, voltage regulator 64 (U20) isconnected to BUFIN (pin 1) of the RMS-to-DC convertor 65. The voltageregulator 64 receives +12V2 that is supplied on connector J11 from thepower supply (FIG. 2K) and converts this 12 volt input voltage to aregulated output voltage that is output on pin 2 of regulator 64.Resistors 441 (R113), 444 (R113), and 447 (R112) set the level of aregulated output voltage from regulator 64, where variable resistor 450(VR11) provides a means to adjust the output current and set the 0 dBreference level for converter 65 of this regulator. Typically, thevoltage regulator 64 is a standard “off-the-shelf” IC, such as a LM317manufactured by National Semiconductor Corporation

[0085] Coupled to output offset (pin 4) and analog common (pin 3) of theRMS-to-DC convertor 65 is a voltage regulator 66 (U21) that alsoreceives the +12V2 voltage from the power supply. The voltage regulator66 provides a +5 volt output that is also supplied to the positive input(pin 3) of amplifier 67. Voltage regulator 66 is typically a standard“off-the-shelf” IC, such as a LM78L05CM.

[0086] RMS output (pin 11) of the RMS-to-DC convertor 65 is provided tothe positive input (pin 5) of amplifier 63 through resistor 453 (R102).Averaging capacitor 464 (C75) is connected across pins 11 and 10 ofconvertor 65 and is used to determine the averaging error that occursduring the calculation of the true RMS of the input signal supplied topin 15 of the convertor 65. The magnitude of the error is dependent onthe value of capacitor 464. As shown in FIG. 2J, the RMS output from pin7 of amplifier 63 is forwarded by way of pin 2 of connector J11 to theI/O board shown in FIG. 3(b) and the micro-controller shown in FIG.3(a). Typically amplifiers 63 and 67 are standard “off-the-shelf” ICs,such as a LM6132AIM.

[0087] The dB output signal at J11 pin 1 (FIG. 2J) has a 50 dB dynamicrange, a 0-5V DC scale for direct input to the micro-controller, and anaccurate linear dB format. These provide an elimination of the need forexpensive DSP processors or math coprocessors, a limitation or reductionof the memory requirements for data and code, and because of theaccurate analog preprocessing, an elimination of the need for elaboratesignal analysis or data conversion algorithms. In addition, a reductionof signal processing time is also provided, as well as reduced processorclock speeds which in turn lowers power consumption. It should be notedthat this invention performs real time analog signal processing on theheterodyned signal only.

[0088] Turning now to FIG. 2K, therein shown is an audio amplifier thatis used to provide an audio output signal that is supplied to a pair ofheadphones connected to the jack 88 (J12) on the rear panel of thehousing (FIG. 7).

[0089] As stated previously, the audio signal on line 304 is applied toone input of the inputs of the summing amplifier 68. An input alarmsignal is supplied to the second input of the summing amplifier throughcapacitor 509 (C62), resistors 500 (R90), 503 (R91), and variableresistor 506 (VR15). Voltage follower amplifier 69 (U15A) utilizes the+12V voltage from the power supply to create a 6 volt reference level(pin 1) that is supplied to the positive input (pin 5) of summingamplifier 68.

[0090] The output signal from the summing amplifier 68 is applied toaudio amplifier 40 (U16) which is transformer coupled by transformer 41(T1) to the jack 88 on the rear panel of the housing (FIG. 7). Controlof the audio volume is achieved by a signal VOL that is provided onconnector J7 through resistors 518 (R96), 521 (R97) to pin 4 ofamplifier 40. In preferred embodiments, amplifier 40 is a standard“off-the-shelf” IC, such as a TDA7052A manufactured by PhilipsSemiconductors.

[0091] FIGS. 9(a) and 9(b) are block diagrams of an additional aspect ofthe invention. In FIG. 9(b), a digital camera 90 is used to make apicture of the device being ultrasonically measured. The camera 90 istypically mounted on the detector housing (FIG. 9(a)). The picturesignal and the signal from the dual heterodyne circuit may be combinedin a circuit 75, but the camera may be activated independently of thesystem. The combiner 75 may be connected to a printer 76 and transmitsprint information directly to the printer from a user in a manner thatis known. In preferred embodiments, the camera is a digital camera thatstores image files. Thus, pictures of the device under test may beprinted, as well as text results.

[0092] In certain embodiments, the camera utilizes a laser beam topinpoint the location of the image. The recorded image is then “coupled”or “linked” to the stored information for that location, e.g.,ultrasonic data, WAV file, and atmospheric conditions. The recordedimage and the stored information for the image location is then uploadedto a suitable portable storage device in the instrument, such as a flashcard 83 (FIG. 4 and FIG. 6), smart media or memory stick. The recordedimage and the stored information is then downloaded to a data basecomputer and incorporated into a data base program that generates areport for determining the condition of the device being measured.

[0093] With specific reference to FIG. 9(b), when an ultrasonicmeasurement of a device is performed, a picture can be captured andstored in memory using the camera 77. The picture can then be forwardedto micro-controller 80 where it is combined with the WAV and line outputfrom the second heterodyne circuit 32 (see FIG. 1) in combiner 75 foroutput to the printer 76. In preferred embodiments, the printoutcomprises a spectral display of the line output and a graphical displayof the WAV file information from the second heterodyne circuit 32 (seeFIG. 1), as well as a picture of the device under test.

[0094] With reference to FIG. 3(a), sensitivity encoder 100 is used toincrease or decrease the sensitivity level of the dual heterodynecircuit in accordance with the present invention. As shown in FIGS. 6and 7, the sensitivity is adjusted by turning a rotational knob 72 thatis located at the back of the housing. In preferred embodiments, thesensitivity encoder 100 is a rotational optical encoder.

[0095] Rotation of the sensitivity encoder 100 by way of knob 72 changesa signal on P24 (FIG. 3(b) which causes D/A converter 71 to the changethe output level of the control voltage VOS 302 on connecter J13 (FIG.3(b)) that controls the gain of VCA 14 (see FIG. 2A). Consequently,changes in the gain of VCA 14 produce proportional changes in thesensitivity level of the dual heterodyne circuit.

[0096] With reference to FIG. 7, LCD 82 provides a display of data thatis used to distinguish between trends or deviations in readings. As aresult, a user is provided with the means to bypass valve analysis andpinpoint an ultrasonic source, such as an internal leak in a tank orvessel, or an underground leak in gas piping or electrical transmissionlines.

[0097] Sensitivity level indicator 105, shown on the LCD 82, providesthe user with the ability to view the sensitivity level setting of thedual heterodyne circuit. As a result, the user can consistently set thesensitivity level of the circuit to permit repeated comparativefrequency spectrum measurements, where repeatability is critical. Asshown in FIG. 7, LCD 82 displays the sensitivity level setting as arange of integer numbers. In the preferred embodiment, this range isfrom 0 to 70, where S is an abbreviation for sensitivity.

[0098] In accordance with the invention, the integer numbers representthe adjustment range of VCA 14 (FIG. 2A), where each integer valuecorresponds to one decibel in the change of the gain of VCA 14. Inaccordance with the preferred embodiment, a sensitivity level setting of70 corresponds to maximum sensitivity while a sensitivity level settingof 0 corresponds to a minimum sensitivity setting (70 dB below maximumsensitivity). In accordance with the invention, the sensitivity settingis also a field in the memory of the portable ultrasonic detector sothat when the user presses the store button 85, the sensitivity levelsetting value is stored. In certain embodiments of the invention, theuser can also annotate data files that are stored, and by way of voicerecognition incorporate them into a final report.

[0099] In accordance with the invention, “Spin and Click™” controls areused to provide an end user interface that is simple and intuitive. Withreference to FIG. 7, knob 72 acts as a cursor control. As knob 72 isclicked, the cursor moves in a set pattern around the display screen 82.If a “function field” is blinking, knob 72 is then spun to change thevalues within the function field. Once a function is selected, knob 72is then clicked to set the selected value.

[0100] In accordance with the preferred embodiment of the invention,multiple applications can be displayed. In the preferred embodiment, 6applications can be displayed, i.e., GENERIC, LEAKS, STEAM TRAPS,VALVES, BEARINGS AND ELECTRICAL. Each application has two screens, i.e.,MAIN and STORAGE. In addition, the screens VALVES AND BEARINGS have anABCD SCREEN. The “Click” on knob 72 moves the “cursor” to “FIXED”positions on each screen. In certain embodiments, the number of controlsare minimized. In the preferred embodiment, two controls are used topermit the user to “navigate” through the various display screens, andchange multiple operational settings.

[0101]FIG. 10 is an illustration of an exemplary network of pipingincluding valves that can be tested with the portable ultrasonicdetector of the present invention. FIGS. 11(a) and 11(b) represent aflow chart illustrating the steps of the method of the invention. Inaccordance with the invention, the method is implemented by performing avisual inspection of valve 117 (see FIG. 10) to confirm that it isclosed or in the off position, as indicated in step 1100. If the valve117 is not closed (step 1105), then the operator closes the valve, andproceeds to the next step where a base line measurement for the valve117 is established, as indicated in step 1110.

[0102] In accordance with the method of the invention, the ultrasound ismeasured at multiple points upstream and downstream from the valve. Inthe preferred embodiment, two upstream points A, B and two downstreampoints C, D are measured. With reference to FIG. 10, the first upstreammeasurement point A is at a distance located X times the pipe diameterfrom the valve. The second upstream measurement point B is locateddirectly upstream from the valve, approximately at the pipe fitting. Inaccordance with the method of the invention, the two downstreammeasurement points C, D are at a distance of equal relationship to theupstream test points, i.e., the first downstream measurement point C islocated directly downstream from the valve, approximately at the pipefitting, and the second downstream measurement point D is at a distancelocated X times the pipe diameter from the valve. In the preferredembodiment, X is six (6). In other words, the first measurements points(A upstream or D downstream) are located at a point that is 6 times thediameter of the pipe 120 away from the valve.

[0103] While touching a contact module to a measurement point to measurethe ultrasonic energy at the two upstream points, the sensitivity of thedual heterodyning circuit is adjusted by turning the rotary knob 72 onthe rear of the portable device so that the LCD 82 displays the dB valueof the ultrasonic measurements. The value of the ultrasound at theseinitial upstream points establishes the baseline measurements for thevalve 117. The ultrasonic measurement at the first and second upstreampoints should be close to each other. In some circumstances, the valueof the ultrasound at the second upstream measurement point can beslightly lower than the value of the ultrasound at the first upstreammeasurement point. In contemplated embodiments, the second measurementis performed without re-adjusting the sensitivity of the dual heterodynecircuit.

[0104] The first of two downstream test points C, D is then measured toobtain the level of the ultrasound at this downstream test point C, asindicated in step 1115. The value of the ultrasound at the firstdownstream test point C is compared to the values of the ultrasound atthe upstream test points A, B, as indicated in step 1120.

[0105] The ultrasound at the second downstream test point D is measuredto ensure that no ultrasonic sound is emanating downstream from thevalve 117, as indicated in step 1130. The value of the ultrasound at thefirst downstream test point C is compared to the values of theultrasound at the second downstream test point D, as indicated in step1140. If the value at test point D is less than the value at C, thevalve is leaking.

[0106] If the value of the ultrasonic sound measured at the seconddownstream point D is greater than the value of the ultrasonic soundmeasured at the first downstream point C, then an attempt should be madeto “tune out” or “shut off” this ultrasonic sound to obtain a propertest of the valve, as indicated in step 1150. The ultrasonic sound maybe “tuned out” or shut of by simply locating source of the sound, andtaking measure to eliminate it, such as closing valve 150 in FIG. 10.When it is determined in step 1160 that it is not possible to tune outor shut off a downstream structure borne ultrasound, it is necessary tolocate the source of the highest reading to determine its effect on theoutcome of the measurements. To accomplish this, an additionalmeasurement of the ultrasound at a measurement point E is performed toassist in locating/confirming the source of the ultrasound, as indicatedin step 1170. Hence, if it is determined in step 1180 that the value ofthe ultrasound at the downstream point E is higher than the values ofthe upstream points A, B, then the valve 117 is leaking, and measuresare taken to correct the leak, such as by replacing the valve, asindicated in step 1190. If in step 1180 it is found that the value ofthe ultrasound at point E is lower than the value of the ultrasound atpoint the upstream points, the valve is operating properly and does notneed to be replaced (step 1195).

[0107] If it is determined in step 1160 that it is possible to eliminatetune out or shut off a downstream structure borne ultrasound, the valueof the ultrasonic sound at the upstream point D is re-measured, asindicated in step 1200. A comparison of the value so the ultrasonicsound at the downstream points D and C is made, as indicated in step1210. If the value of the ultrasound at downstream point D is less thanthe value of the ultrasound at downstream point C, the valve is leakingand must be changed, as indicated in step 1220. On the other hand, ifthe value of the ultrasound at downstream point D is greater than thevalue of the ultrasound at downstream point C, the valve is not leakingand does not need to be changed, as indicated in step 1230.

[0108] If the values of the ultrasound at the downstream points C, D areclose to or lower than the values of the ultrasound at the upstreampoints A, B, then the valve 117 is not leaking, i.e., the valve is good,as indicated in step 1125 (see FIG. 11(a).

[0109] In accordance with the invention, if the valve is workingproperly, then downstream baseline decibel values are recorded andstored in memory for subsequent comparisons to determine whether thevalve is developing a leak. This is accomplished by re-measuring theultrasonic energy at the downstream locations and comparing the energyto the original downstream baseline decibel values. If the ultrasonicenergy at the re-measured downstream locations is greater than the valueof the downstream baseline values, then the valve is developing a leak,and measures can be taken to correct the problem, such as replacing thevalve.

[0110] In an alternative embodiment of the invention, where it is notpossible to use multiple upstream and downstream test point,measurements are performed immediately upstream from the valve. Ameasurement is then performed at a test point directly on the body ofthe valve. In this manner, upstream values are obtained and comparedwith the subsequent downstream valves to determine whether the valve isleaking or not.

[0111] In accordance with the contemplated embodiments of the invention,the ultrasonic sound at the valve measurement points is recorded anddownloaded to a computer using software. In the preferred embodiment, atape recorder is used to record the ultrasound, and the software programis Spectra™. In alternative embodiments, the ultrasonic sound at thevalve test points is recorded directly to a vibration analyzer toobserve the amplitude of the ultrasonic signal at each measurementpoint.

[0112] The dual heterodyning circuit of the present invention providesan enhanced output spectrum. As a result, it is easier to determinewhether the resonance is mechanical or electrical. In addition, faultfrequencies are also more easily detected. The enhanced signal outputprovides a lower signal-to-noise ratio, so as to increase the ease withwhich frequency components are analyzed. The method of the inventionpermits a user of the portable ultrasonic device to quickly and easilydetermine whether a valve is leaking or not

[0113] In addition, the method of the invention eliminates theunnecessary replacements of “good” valves, which can be expensive incertain environments, such as in a nuclear plant or on a ship, where thevalves are welded into place, by permitting a user to quickly and easilydetermine whether a valve faulty.

[0114] Although the invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example, and is not to be taken by way of limitation.The spirit and scope of the present invention are to be limited only bythe terms of the appended claims.

What is claimed is:
 1. A method for processing ultrasonic signals tolocate faulty components in a system using a portable ultrasonicmeasuring device, comprising the steps of: performing a visualinspection of a device in the system to ensure that the component isclosed; measuring ultrasonic energy levels at multiple upstreamlocations at fixed distances from the device to establish baselineultrasonic energy values for the component while the system isoperational; measuring ultrasonic energy at locations downstream fromthe device; comparing a first measured downstream ultrasonic value tothe baseline ultrasonic energy values; measuring a second downstreamultrasonic energy if the first measured downstream ultrasonic energyvalue is greater than the baseline ultrasonic energy values; comparingthe second measured downstream ultrasonic energy to the first measureddownstream ultrasonic energy; and eliminating a downstream source ofultrasonic energy if the second measured downstream ultrasonic energy isgreater than the first measured downstream ultrasonic energy todetermine whether the device is faulty.
 2. The method of claim 1,wherein said component is an on/off valve.
 3. The method of claim 1,further comprising the step of closing the component; and returning tosaid establishing step.
 4. The method of claim 3, wherein the ultrasonicenergy level at two upstream locations is measured.
 5. The method ofclaim 4, wherein a first upstream location is a predetermined distancefrom the component and a second upstream location is directly at thecomponent.
 6. The method of claim 5, wherein the predetermined distanceis an integer value multiplied by a diameter of a pipe in the system. 7.The method of claim 6, wherein the integer is
 6. 8. The method of claim1, wherein said establishing step is performed while adjusting asensitivity level of the portable ultrasonic measuring device; whereinthe sensitivity level of the portable ultrasonic device is adjusted suchthat a dB value of the ultrasonic energy is displayed on a display ofthe portable ultrasonic device.
 9. The method of claim 1, wherein saidstep of measuring ultrasonic energy at downstream locations comprisesthe steps of: measuring the ultrasonic energy level at a firstdownstream location that is a predetermined distance from the component;and measuring the ultrasonic energy level at a second downstreamlocation directly at the component.
 10. The method of claim 9, whereinthe predetermined distance is an integer value multiplied by a diameterof a pipe in the system.
 11. The method of claim 10, wherein the integeris
 6. 12. The method of claim 1, further comprising the steps of:measuring ultrasonic energy at an additional downstream point to locatean ultrasonic sound source.
 13. The method of claim 1, furthercomprising the step of: recording downstream baseline decibel values;and storing the downstream baseline values in memory for comparisonswith future downstream baseline values to determine whether thecomponent is leaking.
 14. The method of claim 13, further comprising thestep of: re-measuring the downstream baseline decibel values; retrievingthe stored baseline decibel values from the memory; and comparing theretrieved baseline decibel values to the re-measuring the downstreambaseline decibel values; and replacing the component if the re-measureddownstream baseline decibel values are greater than the retrievedbaseline decibel values.
 15. The method of claim 8, wherein thesensitivity is adjusted by turning a knob located on a rear panel of theportable ultrasonic measuring device, said knob also permittingnavigation between various display screens on a display of theapparatus.